Pentylenetetrazol, also known as pentylenetetrazole, leptazol, metrazol, pentetrazol (

INN Inns are generally establishments or buildings where travelers can seek lodging, and usually, food and drink. Inns are typically located in the country or along a highway; before the advent of motorized transportation they also provided accommo ...

), pentamethylenetetrazol, Corazol, Cardiazol, Deumacard, or PTZ, is a drug formerly used as a circulatory and respiratory stimulant. High doses cause

convulsions A convulsion is a medical condition where the body muscles contract and relax rapidly and repeatedly, resulting in uncontrolled shaking. Because epileptic seizures typically include convulsions, the term ''convulsion'' is sometimes used as a s ...

, as discovered by Hungarian-American neurologist and psychiatrist

Ladislas J. Meduna Ladislas Joseph Meduna (27 March 1896 – 31 October 1964), a Hungarian neuropathologist and neuropsychiatrist, initiated convulsive treatment, the repeated induction of grand mal seizures in the treatment for psychosis. Observing the high concentr ...

in 1934. It has been used in convulsive therapy, and was found to be effective—primarily for depression—but side effects such as uncontrolled

seizure An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with los ...

s were difficult to avoid. In 1939, pentylenetetrazol was replaced by electroconvulsive therapy, which is easier to administer, as the preferred method for inducing seizures in England's mental hospitals. In the US, its approval by the

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...

was revoked in 1982. It is used in Italy as a cardio-respiratory stimulant in combination with

codeine Codeine is an opiate and prodrug of morphine mainly used to treat pain, coughing, and diarrhea. It is also commonly used as a recreational drug. It is found naturally in the sap of the opium poppy, ''Papaver somniferum''. It is typically use ...

in a

cough suppressant Cold medicines are a group of medicinal, medications taken individually or in Combination drug, combination as a Symptomatic treatment, treatment for the symptoms of the common cold and similar conditions of the upper respiratory tract. The t ...

drug.

Mechanism

The mechanism of pentylenetetrazol is not well understood, and it may have multiple mechanisms of action. In 1984, Squires et al. published a report analyzing pentylenetetrazol and several structurally related convulsant drugs. They found that ''in vivo'' convulsant potency was strongly correlated to ''in vitro'' affinity to the picrotoxin binding site on the

GABA-A receptor The GABAA receptor (GABAAR) is an ionotropic receptor and ligand-gated ion channel. Its endogenous Ligand (biochemistry), ligand is γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system. Upon opening, ...

complex. Many GABA-A ligands, such as the sedatives diazepam and phenobarbital, are effective

anticonvulsants Anticonvulsants (also known as antiepileptic drugs or recently as antiseizure drugs) are a diverse group of pharmacological agents used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of b ...

, but presumably pentylenetetrazol has the opposite effect when it binds to the GABA-A receptor. Several studies have focused on the way pentylenetetrazol influences neuronal ion channels. A 1987 study found that pentylenetetrazol increases calcium influx and sodium influx, both of which depolarize the neuron. Because these effects were antagonized by calcium channel blockers, pentylenetetrazol apparently acts at calcium channels, and it causes them to lose selectivity and conduct sodium ions, as well.

Research

Pentylenetetrazol has been used experimentally to study seizure phenomena and to identify pharmaceuticals that may control seizure susceptibility. For instance, researchers can induce

status epilepticus Status epilepticus (SE), or status seizure, is a single seizure lasting more than 5 minutes or 2 or more seizures within a 5-minute period without the person returning to normal between them. Previous definitions used a 30-minute time limit. The s ...

in animal models. Pentylenetetrazol is also a prototypical

anxiogenic An anxiogenic or panicogenic substance is one that causes anxiety. This effect is in contrast to anxiolytic agents, which inhibits anxiety. Together these categories of psychoactive compounds may be referred to as anxiotropic compounds. Anxiogen ...

drug and has been extensively used in animal models of

anxiety Anxiety is an emotion which is characterized by an unpleasant state of inner turmoil and includes feelings of dread over anticipated events. Anxiety is different than fear in that the former is defined as the anticipation of a future threat wh ...

. Pentylenetetrazol produces a reliable

discriminative stimulus In behavioral psychology (or applied behavior analysis), stimulus control is a phenomenon in operant conditioning (also called contingency management) that occurs when an organism behaves in one way in the presence of a given stimulus and another w ...

, which is largely mediated by the GABA_A receptor. Several classes of compounds can modulate the pentylenetetrazol discriminative stimulus, including 5-HT_1A, 5-HT₃, NMDA, glycine, and

L-type calcium channel The L-type calcium channel (also known as the dihydropyridine channel, or DHP channel) is part of the high-voltage activated family of voltage-dependent calcium channel. "L" stands for long-lasting referring to the length of activation. This c ...

ligands In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electro ...

References

{{Convulsants Antidepressants Stimulants GABAA receptor negative allosteric modulators Withdrawn drugs Respiratory agents Convulsants Tetrazoles

Mechanism

Research

See also

References